Sexual chemistry is something that happens immediately when you meet someone in the real world for the first time. Not all sexual chemistry is a wildfire of "let's get it on." But most of the sexual tension and sexual awareness comes from recognizing your own desire, your own needs, and how you imagine this person fitting in and even pushing the envelope a bit.
Be good to yourself. Love yourself and your partner (if you have one) as best you can. Gain mindfulness in all aspects of your life. And get into the FLOW of your life and of your relationship.